David Kostin, chief U.S. equity strategist at Goldman Sachs, raised his 2014 year-end target on the benchmark S&P 500 from 1,900 to 2,050. That's because he lowered his forecast on U.S. Treasury bonds. In a note to investors, Kostin wrote:

"US equities soared 42% during the past 18 months but the stellar return borrowed heavily from the future. History shows S&P 500 rallies and the P/E multiple expands during the year prior to the start of a tightening cycle. But after tightening begins, the multiple contracts and the index typically delivers only modest returns. Incorporating our lower 10-year US Treasury yield forecast with other valuation approaches, we lift our year-end 2014 S&P 500 price target to 2050 (from 1900) and 12-month target to 2075, reflecting prospective returns of 4% and 6%, respectively. Our year-end 2015 and 2016 targets remain unchanged at 2100 and 2200."

Kostin said the bulk of the S&P 500's returns came from earnings growth, and he sees the index's earnings growing at an annual rate of 8 percent. While calling its multiple of 16.5 times forward earnings "high," he sees the index as attractive relative to fixed income, given the low level of bond yields.

However, Richard Ross, global technical strategist at Auerbach believes the technicals on the S&P 500 justify some trepidation.

"It's very difficult to assail the technicals," said Ross, a "Talking Numbers" contributor. "We've been above the 150-day moving average for just about 18 months. That could be our greatest strength and also our Achilles' heel. We're well above that trend for such an unperturbed amount of time; you have to go back to '95 - '96, a similar period of 17 months that we traded without a break of the 150-day moving average. That advance took us up 47 percent. This advance has taken us up 42 percent."

Ross believes there is some technical symmetry between the two advances. A test of the 150-day moving average would bring the S&P 500 down to 1,866.70, about 5.6 percent below current levels.

But the outlook is worse based on the technicals on the five-year chart of the index. In the same way he used the 150-day moving average on the short-term chart, Ross uses a 150-week moving average on the long-term chart.

"We've been above [the 150-week moving average] for quite some time," Ross said. "In fact, you have to go back to that period–1982 to 1987–to find a similar type period from a technical standpoint when we're above trend for so long. And we all know how things ended in 1987."

Finally Ross looks to a third time period: July 15, 2011. Three years ago was when we saw "the last meaningful correction in the S&P 500, which took us down over 20 percent," he said. "There's some technical symmetry here. There's some reason for caution, even against this bullish Goldman call."

Gina Sanchez, founder of Chantico Global, says the fundamental case is not as rosy as Goldman makes it out to be. The economy contracted 2.9 percent in the first quarter, and corporate results were mediocre. The market may be trading as if it will make up the losses throughout the rest of this year, but the International Monetary Fund estimates show that may not happen. Sanchez believes that will be reflected in earnings.

"If you look at FactSet right now, 111 companies have come out with guidance," said Sanchez, a CNBC contributor. "Of those, 84 companies have had negative guidance. That's 76 percent of companies and that's after a weak first quarter. So if you're sort of expecting them to be gaining that back, the guidance isn't suggesting that."

That may hurt companies' ability to buy back stocks, which may in turn negatively impact the market.

"TrimTabs CEO David Santschi came out saying that there is a very high correlation between stock buybacks and a positive market," Sanchez said. "All of these things are telling you that there's reason for caution right now–big reasons for caution–and that we really have to think about where the market is going from here."

To see the full discussion on the S&P 500, with Ross on the technicals and Sanchez on fundamentals, watch the above video.